[What happens to our private messages and other chat?]

Not sure about LL policy regarding storage of messages but it does not surprise me that they store them.  This is the way things are done in the era of modern communications.  Most cell phone companies keep an archive of text messages but usually purge them after a short time (week or so?).  I assume LL has some purge policy in place but who knows.  As another poster mentioned I believe  Emerald allows you to encrypt your IMs so if you are really concerned you could go that route.  Also, you can log chat and IMs to your local hard drive so if you need the history for some reason you will have it.

[How Do You Make SLURL Work For Third Party Viewers?]

I think what happens is that the last viewer you installed becomes the default one used when clicking a SLURL.  As noted above this can be changed in the registry.

[Camera view...stuck]

You can adjust the camera settings in preferences under Input & Camera.  Have you tried that?

[How do I run second life from a flash drive, and still save user settings?]

In fact I am able to preserve the settings of my different accounts.  I think this is more a function of the settings file then the cache, so you may be able to keep one cache but just use different settings files...

[How do I run second life from a flash drive, and still save user settings?]

I am pretty sure there is a way to do this. You will need to explore the start up options (http://wiki.secondlife.com/wiki/Client_parameters).  You can specify a local settings file and I believe in there you can set the cache location.  There is also a -set start up option that supposedly lets you set (or override) any parameter in the settings file.  I have used different settings and cache files for running multiple viewers on the same computer successfully but have not tried what you are attempting.